The present invention relates to a turbine ring sector made of ceramic matrix composite material, to a turbine ring assembly intended in particular for use in a turbine engine, and to a method of fabricating such a ring sector.
With turbine ring assemblies made entirely out of metal, it is necessary to cool all of the elements of the assembly, and in particular the turbine ring, which is subjected to the hottest streams. Such cooling has a significant impact on the performance of the engine, since the stream used for cooling is taken from the main stream through the engine. Also, using metal for the turbine ring limits the potential for increasing temperature within the turbine, even though that would serve to improve the performance of aeroengines.
In an attempt to solve those problems, it has been envisaged to make turbine ring sectors out of ceramic matrix composite (CMC) material in order to avoid using a metal material.
CMC materials present good mechanical properties, making them suitable for constituting structural elements, and advantageously they conserve those properties at high temperatures. Using CMC materials has advantageously made it possible to reduce the cooling stream that needs to be delivered in operation, and thus to improve the performance of turbine engines. Also, the use of CMC materials serves advantageously to reduce the weight of turbine engines and to reduce the effect of expansion when hot, as encountered with metal parts.
In the operating conditions of aviation turbine engines, characterized in particular by high temperatures and an environment that is corrosive, CMC materials can become degraded. In order to protect the portions of the ring sectors that are exposed to the stream of corrosive hot air through the turbine, it is known to coat such parts with an environmental barrier (or an environmental barrier “coating” (EBC)). For example, there are known multi-layer environmental barriers of the Si/Mullite/BSAS type (where BSAS is barium and strontium aluminosilicate), or indeed those including a silicon bonding layer and a layer of a rare earth silicate (e.g. Y2Si2O7). In known manner, environmental barriers may be deposited by thermal spraying methods, by physical vapor deposition (PVD) methods, or by depositing slurries (e.g. by dip coating or by spray coating).
In each ring sector, the faces between sectors (“inter-sector” faces) generally include slots that receive sealing tongues, serving to prevent gas leaking to the outside of the flow passage for the gas stream through the turbine. These slots, which constitute shapes that are said to be “blind”, can be formed by conventional machining methods.
Nevertheless, it would be desirable to simplify forming slots in the inter-sector faces of the ring sectors.